Stable emulsions or suspensions of rubbers in aqueous mediums are useful in many applications. Water base paints, adhesives, and rust proof coatings, are examples of such applications. Water based systems are advantageous over systems utilizing hydrocarbon solvents because of the environmental and safety impact of vaporizing hydrocarbon solvents. Water based systems also are generally more economical due to the expense of hydrocarbon solvents.
Emulsions or suspensions of rubbers in aqueous mediums may be formed by mixing rubbers containing solvents in high speed dispersers. This is usually accomplished with the aid of a viscosity control agent and a surfactant. Solvents, monomers, or softening oils are typically required to result in a dispersion which is of a particle size which is sufficiently small to ensure that the particles remain in suspension. Such a process is disclosed in U.S. Pat. No. 4,282,131. The presence of solvents is acceptable in some applications, but it is desirable in other applications to provide a suspension of rubber in which the rubber does not contain solvents.
It is therefore an object of the present invention to provide a process to prepare an aqueous dispersion of a block copolymer wherein the block copolymer does not require softening by addition of processing oil, solvent, or monomers. In another aspect, it is an object to provide a process to prepare an aqueous dispersion of a block copolymer wherein the dispersion is stable. In another aspect, it is an object to provide a composition comprising an aqueous continuous phase and a stable dispersion of block copolymer particles.